Exhaust valve



Sept. 10, 1929. TAUB 1,727,621

EXHAUST VALVE File d Feb. 18. 1928 Patented Sept. 10, 1929.

UNITED STATES PATENT OFFICE.

ALEX TAUB, OF DETROIT, MICHIGAN, ASSIGNOR TO GENERAL MOTORS CORPORATION,

' OF DETROIT, MICHIGAN, A CORPORATION OF DELAWARE.

EXHAUST VALVE.

Application filed February 18, 1928. Serial No. 255,428.

This invention relates to an internal combustion engine of the poppetvalve type and more particularly to an exhaust valve.

In a conventional poppet valve engine the head of the exhaust valveseats over the exhaust opening and is carried by a stem extending acrossthe exhaust passage and through a guide in the engine block or cylinderhead. Since the temperature within the exhaust passage remains at about14:00 to 1700 degrees F. at ordinary engine speeds, the exhaust gaseshave a very destructive effect on that part of the valve stem within theexhaust passage, causing corrosion or 15 pitting and producing adestructive change in the structure of the metal of the stem, which maycause the stem to lose its requisite strength, hardness and non-breakingqualities and become warped.

This difiiculty has been met in several ways, such as by making thevalve stem of a special alloy steel, or by using a hollow valve-stem andproviding a cooling fluid in the stem. Eachuof these methods is exensive and adds considerably to the cost 0 the product.

According to the present invention I provide simple and inexpensivemeans for protecting the valve stem from the high tem perature withinthe exhaust passage. I accomplish this by insulating the main portion ofthe stem and head within the exhaust passage from direct contact withthe exhaust gases, the inclusion of a portion of the head 5 in theinsulated zone being an important feature since the amount of heatabsorbed by the valve stem is a function of the area exposed to theheat. While various solid non-metallic insulating media may be em- 4ployed I find that the provision of a dead air space about thestem-connected side of the head and a portion of the stein givessatisfactory results. It is therefore a particular object of theinvention to provide insulating means for a portion of the valve exposedto the high temperature of the exhaust passage so that the valve headand stem will be maintained at a lower temperature than has hithertobeen practicable. By protecting the valve stem so that it will bemaintained at a lower temperature,

a stem of lower grade and hence less expensive metal may {be used withsatisfactory results; the expansion of the valve stem will be less andthe valve clearance may be reduced, and there will be less danger of thevaive sticking as a result of overheating.

Other objects and advantages of the invention will appear in the courseof the following description, taken in connection with the accompanyingdrawing and appended claims.

In the drawing: C J

Figure 1 is a sectional view through a portion of an internal combustionengine as including an exhaust passage, exhaust valve and associatedparts.

Figures 2, 3, 4 and 5 are sectional views of exhaust valves,illustrating modified forms of my invention.

In Fig. 1 is shown a portion of an overhead-valve engine comprising acylinder head 10 which is formed with an exhaust passage 12, waterjacket 14 and valve stem guide 16; Fitted in the guide 16 is a valvestem 18 arrying a valve head 20 which is within the combustion chamber22 and is seated in the usual manner in the opening to the exhaustpassage 12. The valve is controlled in the usual manner by a coil spring24.and a rocker arm 26, as will be understood.

The valve head 20 may be formed with a. circular undercut groove 28 onits stemconnected side. Surrounding the stem within the exhaust passageis a conoidal shroud '30 consisting of a tapered metal stamping thelarge end of which is spun into the groove 28. The shape of the largeend of the stamping before the spinning co operation is indicated indotted lines at 32. The shroud tapers away from'the valve head and fitsthe stem at a point adjacent the end of the guide 16 so that when thevalve is seated, the shroud incloses tractically all the stem which iswithin the exhaust passage and most of the stem-connected side of thevalve head.

In Fig. 2 is shown a valve comprising a head 36 anda stem 38. A circulargroove 40 is formed on the stem-connected side of the valve head, andthe stem is provided with a groove 42 spaced from the valve head.Surrounding the stem is a tapered shroud 44 which comprises a metalstamping the large end of which fits within the groove 40 and the smallend of which is formed within an inward turned flange fitting in thegroove 42. The shroud is snapped into the'position illustrated, beingprovided with opposite axially extending slits 46 for permitting it tobe slipped along the stem until the flanged end registers with andsprings into the groove 42.

In Fig. 3 is shown a valve which comprises a stem 48 f rmed with areduced portion 50 which is t readed to receive a valve head 52, the endof the stem being *peened over at 54 for fixing the head securely on thestem. The length of the reduced portion 50 is about equal to the wldthof the exhaust passage in which the valve is designed to operate, thisconstruction providing an annular shoulder 51 on the stem some distancefrom the head.

The head 52 is .formed on its stem-connected side with an annular ridge56 having a frusto-conical outer surface fitting within the larger endof a tapered shroud 58, the opposite end of the shroud fitting thereduced portion 50 of the valve stem and abutting against the shoulder51. The thickness of the shroud may be equal to the difference betweentheradii of the two parts of the stem, as illustrated, so that theshroud may be extended some distance within the valve stem guide, ifdesired. The shroud is a metal stamping "similar to the stampings 44 and30 described above and may be pressed on the stem before the head, orthe head may be fixed on the stem first and the small end of the shroudspun into its illustrated posi tion against the shoulder 51-.

In Fig. 4 is shown a valve comprising a stem 60 and head 62, the headbeing pro- .v1ded on its stem-connected side with a circular flange ofmalleable metal, -i ndicated in-dotted lines at 64. A shroud 68 sur-frounds the stem with its valve head attachmg end flanged outward, as at70, and

fitting within the flange 64.. The shroud is V fixed to the valve byspinning the flange 64 over the flange 70'of the shroud, as shown 1nfull lines at 66. The opposite end of the shroud has .a reduced diameterand fits the valve stem. f I v In Fig. 5 is shown a valve comprising astem 74 threaded to receive a head 76. The head is a casting cored outto forma web 78 fitting the stem somedistance from the .port closingportion of the head, thereby providing an inclosed space '80 at thestem-' connected side of the head. The end of the stem is peened over at82 to hold the head securely on the stem.

In the form of my invention shown in Figs. 1, 2, 3 and 4, the metalstamping (30, 44, 58 or 68) provides an inclosed space about thestembeneath the valve head for a distance corresponding roughl width ofthe exhaust passage 0 the engine. The stamping thus provides a dead airspace which serves to insulate from direct contact with the hot exhaustgases that portion of the stem andthe side of the valve head which arewithin the exhaust passage. A similar result is attained by providingthe cored" out valve head shown in Fig. 5. The shroud need not providean airtight space and should not, since the pressures inside and outsidethe shroud should remain equal. The stampings may be made from deepdrawing stock which will retain its shape' vwhile exposed to the hot.exhaust gases.

The main feature of the constructions shown is the provision of aninsulator about part of the valve stem and the exhaust port side of thevalve head. Since the exhaust gases do not come into direct contact withthat part of the valve which is inclosed by the shroud and since a gasis a very poor conductor of heat, nearly all the heat trans mitted tothe inclosed part of the valve is b radiation from the shroud, only i asm amount being transmitted by conduction from the ends of the shroud.The air in the inclosed air space thus constitutes a nonmetallicinsulating medium that retards very considerably the passage of heatfrom the exhaust gases into the valve. As the valve guide is formed in aweb of the cylinder head or engine block which-is-water cooled, heat isnot permitted to accumulate in the valve stem but is dissipatedrapidly,'and the valve stem is maintained at a much lower temperaturethanit would be if the insulatin means were not provided.

ince the stem is maintained at a reduced temperature, the elongation dueto heating will be less and a less valve clearance will be required, astem of lower quality steel will be satisfacto the usual higtemperatures, and the probability of the valve stem becoming stuck intheguide will be lessened.

.I claim: Y

1-. A poppet valve comprising a stem and a head, and formed with aninclosed space at the stem-connected side of said head," and a metallicconnection'between said head and stem within said inclosed space.

2. A poppet valve comprising a head and with the since it need notwithstand a stem, and a shroud extending from said 4 head to a point onthe stem spaced from saidvhead.

3. A poppet valve comprising a head and a stem, and a sheet metal shroudinclosing- 4. A poppet valve comprising a stem and a head, and a shroudconnected With the stem-connected sideof said head and fitting said stemat a point spaced from said head.

5. In an internal combustion engine including an exhaust passage, avalve comprising a stem and a head" positioned to close said passage,and means for insulating a portion of the under side of said head fromdirect contact With the exhaust gases.

In testimony whereof I aflix my signature.

ALEX TAUB.

